FMOS near-IR spectroscopy of Herschel selected galaxies: star formation rates, metallicity and dust attenuation at z~1

TL;DR

This study uses near-infrared spectroscopy to analyze Herschel-selected galaxies at z~1, revealing their star formation, metallicity, and dust properties, and how these relate to each other and compare to local galaxies.

Contribution

It provides new measurements of dust attenuation, star formation rates, and metallicity for infrared luminous galaxies at z~1 using FMOS spectroscopy, expanding understanding of galaxy evolution.

Findings

Dust attenuation correlates with star formation rate.

IR-selected galaxies at z~1 follow the local mass-metallicity relation.

Metal-rich galaxies exhibit higher dust attenuation.

Abstract

We investigate the properties (e.g. star formation rate, dust attentuation, stellar mass and metallicity) of a sample of infrared luminous galaxies at z \sim 1 via near-IR spectroscopy with Subaru-FMOS. Our sample consists of Herschel SPIRE and Spitzer MIPS selected sources in the COSMOS field with photometric redshifts in the range 0.7 < z-phot < 1.8, which have been targeted in 2 pointings (0.5 sq. deg.) with FMOS. We find a modest success rate for emission line detections, with candidate H{\alpha} emission lines detected for 57 of 168 SPIRE sources (34 per cent). By stacking the near-IR spectra we directly measure the mean Balmer decrement for the H{\alpha} and H{\beta} lines, finding a value of <E(B-V)> = 0.51\pm0.27 for <LIR> = 10^12 Lsol sources at <z> = 1.36. By comparing star formation rates estimated from the IR and from the dust uncorrected H{\alpha} line we find a strong relationship between dust attenuation and star formation rate. This relation is broadly consistent with that previously seen in star-forming galaxies at z ~ 0.1. Finally, we investigate the metallicity via the N2 ratio, finding that z ~ 1 IR-selected sources are indistinguishable from the local mass-metallicity relation. We also find a strong correlation between dust attentuation and metallicity, with the most metal-rich IR-sources experiencing the largest levels of dust attenuation.